Various technologies have been developed to deliver bioactive agents to a vessel wall for treating a variety of medical indications. One example involves the application of an anti-restenosis agent to a vessel wall following or sometimes during an angioplasty procedure. Another example is in the localised treatment of tumours.
One technology involves the use of a drug coated medical balloon, which is inflated against the vessel wall in order to bring the bioactive agent into contact with the vessel tissue for transfer of the bioactive agent into the affected tissue. This may be by way of elution from the balloon, by injection through apertures or pores in the balloon, from simple transfer of the bioactive agent from the balloon surface, and so on. It is also known to use one or more medical balloons to stop blood flow in the vessel, which in effect closes off the vessel, and then to inject bioactive agent into the vessel or otherwise administer bioactive agent into the vessel while the vessel is blocked.
A problem with such medical balloons is that they choke off blood supply from organs downstream of the balloon, and as a result any procedure involving such balloons is time limited.
Attempts have been made to overcome the limitations of such balloons, by developing balloons having an internal lumen which allows continued passage of blood through the balloon. Such balloons could be described as having an elongate doughnut shape. These balloons, however, have a significant deflated volume, which reduces their compressibility and flexibility, leading to challenges in their endoluminal delivery to the treatment site. It also makes such balloons unsuitable for treating small diameter vessels including the cerebral vessels. The lumen through the balloon is also necessarily restricted, leading to reduced blood flow in the vessel.
It is also known to have drug coated stents which are implanted into the vessel. While stents will not generally impinge on the flow of blood through the vessel, they result in a foreign object being left in the patient, either permanently or until the stent is removed during a second medical procedure.
Some examples of devices for administering drugs into a vessel of a patient are disclosed in U.S. Pat. Nos. 7,641,844, 8,226,603, US-2001/0035456, US-2007/0207179, US-2002/0090388 and US-2002/0010418, the contents of which are incorporated by reference.